1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to an n-type Schottky barrier tunnel transistor (SBTT) and a manufacturing method thereof.
2. Description of the Related Art
As a semiconductor device is microminiaturized in its size, a leakage current due to a short channel effect is remarkably increased and an operation characteristic of the semiconductor device is deteriorated. To overcome these problems, lots of researches are under progress. For one of examples, an SBTT may be suggested.
The SBTT may be recognized as a device having a possibility of solving a problem caused by a shallow junction between a source/drain electrode and a channel which is a crucial technical factor for suppressing the short channel effect as a metal oxide semiconductor field effect transistor (MOSFET) is currently scaled down, and additionally solving a problem caused by a gate oxide layer.
In the n-type SBTT, rare-earth metal silicide formed by having rare-earth metal react to silicon (Si) may be used for the source and the drain electrodes. The rare-earth metal silicide has a small work function and thus has a considerably small Schottky barrier with respect to the silicon. Therefore, the rare-earth metal silicide may be considered as having a large saturated current compared with transition metal silicide. Nevertheless, the rare-earth metal silicide may show a very weak thermal stability but shows a large electric specific resistance and thus is examined as having a small saturated current substantially.
Studies on forming a source and a drain of the n-type SBTT of a related art have been primarily concentrated on forming a rare-earth metal silicide of a single layer by performing a thermal treatment after depositing rare-earth metal having a small work function on a silicon substrate. Nevertheless, when forming the source and the drain with the rare-earth metal silicide of the single layer, an electric resistance is relatively large, whereby a larger saturated current cannot be obtained. Therefore, to overcome this disadvantage, it is very important to reduce a parasitic resistance that might be unnecessarily generated due to a large electric specific resistance without destroying a small Schottky barrier between the source and the drain formed with the rare-earth metal silicide.